1. Field of the Invention
This invention relates in general to printing presses, and in particular to an apparatus for preventing contact of wet ink on printed sheets with the printing press chain delivery mechanisms.
2. Description of the Prior Art
In printing presses with chain delivery mechanisms, the sheet is drawn between a blanket cylinder and an impression cylinder, then gripped by a chain delivery mechanism and pulled rearwardly where it is deposited in a stack. The chain delivery mechanism has a pair of sprockets mounted next to the impression cylinder. A chain extends around each of the sprockets and has horizontal upper and lower runs. A gripping mechanism is mounted to the chains for gripping the leading edge of the sheet as it passes through the impression cylinder. The sprockets are mounted on a shaft that is parallel with the axis of the impression cylinder.
A long standing problem is avoiding contact of the wet ink on the sheets with the shaft that extends between the two sprockets. Any contact of the shaft with the ink will likely cause smearing. One system to avoid smearing comprises placing small wheels on the shaft. There are several different wheel designs. The wheels are preferably positioned to contact the sheet where no ink is deposited. This is not always possible. In sheets with an extensive amount of ink coverage, the wheels will contact the ink and cause smearing. Other devices have been proposed and used but not entirely satisfactorily.